The measurement principle of the present invention is based on the one hand on the measurement of a magnetic field produced by the current to be measured which is called the primary current and on the other hand on the measurement of an auxiliary magnetic field produced by a secondary current flowing through a coil. The current sensor therefore comprises a magnetic field sensor, such as e.g. a Hall device, a fluxgate sensor or a magnetoresistive sensor like an AMR or GMR sensor. In the prior art, the magnetic field produced by the current to be measured and the auxiliary magnetic field produced by the secondary current flowing through the coil run in the same direction and the magnetic sensor is a single axis sensor the sensitive axis of which is collinear with this direction. The prior art distinguishes mainly between two different implementations of this measurement principle. With the first implementation which is called open-loop type, the auxiliary magnetic field is used to calibrate the magnetic field sensor. The drawback of this implementation is that the value of the auxiliary magnetic field is low, that the auxiliary magnetic field runs in the same direction as the primary current's magnetic field, which makes it difficult to selectively measure it in a signal comprising both the primary current's magnetic field and the auxiliary magnetic field. With the second implementation which is called closed-loop type the auxiliary magnetic field is used to compensate the magnetic field produced by the current to be measured. An advantage of this second implementation is that the output signal of the current sensor does not depend on the characteristics of the magnetic field sensor but the drawback is that the auxiliary magnetic field must be of equal size as the magnetic field produced by the primary current. A closed-loop current sensor without a magnetic yoke, where the electrical signal containing the information on the measured magnetic field is counterbalanced by the electrical signal containing the information on a reference field created by a current flowing through a reference coil is known from JP 2001136921.